1. Field of the Invention
The present invention relates to a process controlling method and a controller, and more particularly to a method for creating, structuring and executing programs in the controller.
2. Description of the Related Art
A method for combining a ladder program with a flowchart language program is disclosed in "Yaskawa Denki" vol. 53 No. 203 `89.2 (hereinafter referred to as a known example 1)` in which the flowchart language program is activated by the ladder program when a trouble has occurred.
U.S. Pat. No. 4,742,443 (hereinafter referred to as a known example 2) discloses a method for dividing a large control task into a plurality of control steps to be sequentially executed so as to define each control step using a separate ladder program while defining the procedure, according to which the control steps are to be executed, using a structure chart program.
Referring to the known example 1, the ladder program defines the whole flow of a program and the structural form of the program is not taken into consideration. Consequently, the following problems are caused: Even after completion of creating a program, an actual machine test cannot be carried out until the program is installed into a system. It is difficult to execute the parallel work for program development. It is hard to carry out separation of the system when troubles have occurred. Know-how of machine operation and that of production flow are included in the same program so that it is difficult to keep information confidential.
Referring to the known example 2, the program is structured. However, no means for manual control of machines is disclosed. The ladder programs do not include means for manually controlling the machines. Consequently, it is difficult to separate the ladder programs from the flowchart language program so as to execute the actual machine tests of the ladder programs. Furthermore, it is hard to cope with troubles. In addition, the structure chart program and the ladder programs are not to be executed in parallel but to be executed sequentially. Accordingly, it is difficult to perform processes such as management of a waiting time using the structure chart program while executing the ladder programs.